This invention relates to a machine through which bottles are passed for inspection and is particularly concerned with improving the devices for inspecting the side walls of bottles for contamination and flaws.
Inspection machines which transport bottles through a circular path while they are being inspected are well known. Typically, the bottles are deposited on a rotary table and their upper portions are engaged by synchronously driven star wheels for stabilizing the bottles as they are carried through a circular path. Generally, there is a source of a beam of light on one side of the bottles and a photodetector array on the other side of the bottles which delivers a control signal that results in ejection of the bottle if the beam is attenuated or dispersed by a contaminant or a flaw. In any case, it is desirable that the bottles do not shift relative to each other as they are transported through the machine and simultaneously rotated. Problems arise, however, as a result of the requirement that the light or radiation source be on one side of the circular path followed by the bottles and the detectors being on the other side because of the large amount of space that is occupied by the rotors and their driving and bearing elements.
In one known type of bottle inspection machine, an upper rotor, constituted by a starwheel, is fixed on a vertical driven shaft and the lower rotor on which the bottles are carried is coupled to the upper rotor with spacer shafts or tie rods. The upper rotor engages the shoulders of the bottles. With this arrangement, space is provided for an illumination source below and radially within the lower rotor which is located on the side of the drive shaft facing away from the bottle-free area of the rotors. A disadvantage of this arrangement is that the area of the bottle shoulder above the lower rotor cannot be scanned and that the positions of the bottles can change because of the lack of guidance at their bases.
In another type of inspection machine, as in the previously mentioned one, the upper rotor is a starwheel fixed on a vertical drive shaft and the lower rotor is a star ring that is connected to the upper rotor by means of spacer shafts. In this particular machine, however, the lower rotor engages the bottles near their bases and the bottles are positioned on continuous belts for rotation as they advance so scanning accuracy is improved. The scanning device used comprises two oscillating mirrors and two photoelectric sensor arrays which are mounted to the side of the driven shaft facing away from the bottlefree area so that there is the disadvantage of poor accessibility. Moreover, the scanning elements are located in an area where they are particularly endangered by bottle fragments. In this connection, it may be noted that the rotors rotated within the upper portion of a large box type machine housing so that even accessibility from below is greatly restricted. In this and other arrangements there is also the disadvantage of not being able to use a lens system that has a long focal length in which case, in accordance with the laws of optics, the depth of field is small.
In another known type of bottle inspection device there is a lower rotor that carries plates or discs on which the bottles are deposited for being transported in a circular path. The supporting discs are oscillated rotationally to assure that the entire bottle wall is disposed within the scanning beam area. In this case, the upper rotor has vertically reciprocable centering bells which engages the bottles at their upper mouth to stabilize them. Both the upper and lower rotors are secured against rotation relative to each other by means of a hollow cylinder provided with scanning slots lying close to the bottles such that the scanning device is located within the hollow cylinder exactly at the rotational axis of the rotors. Accordingly, the scanning device is accessible only after an extensive disassembly of the machine.
Still another known inspection machine for bottles is provided with one spool-shaped rotor that has rollers on its circumference for engaging on the bottle bodies. This rotor operates together with a band traveling in front of an illumination source. The band has rollers which engages the bottle body. Laid transversely through the rotor and its axis of rotation is a bundle of optical fibers rotating with the rotor. The optical fibers conduct light passing through the bottles to several photoelectric sensors fixedly arranged in the bottle-free area of the rotor. Even in this device, the light conductors forming a part of the scanning device within the interior of the rotor are not easily accessible. These light conductors are, furthermore, subject to physical disturbances and require and expensive and complicated structure to overcome the problem. The same is true for the photodetectors which are almost as large as a bottle circumference. Such large elements are expensive and are notable for having low sensitivity. In this machine, where bottles are pushed along through rollers over a stationary sliding surface, precise and disturbance-free transportation is impossible.
One object of the present invention is to substantially improve the accessibility of the scanning apparatus without loss of inspection accuracy. According to the invention, upper and lower rotors are connected only by coaxial shaft means constituting a column which may have a relatively small diameter. The column is central and coaxial with the rotors and is in an area free of rotating bottles. The bottles are transported in a series along a circular path defined by the rotor. A source of an illumination beam for the bottles is located radially outwardly from the circular path of the bottles and directs two light beams through the bottles in a direction generally toward the central support column for the rotors. In one embodiment, the detectors which receive the light beams that define an image of the bottle wall are diametrically opposite from the source of the light beams. The light beams pass the columns on diametrically opposite sides. In this embodiment, only about 180.degree. of the rotor is occupied by bottles so as to leave an open space on the side of the rotor at which the photodetectors or image detecting means are located. Thus, the two beams from the light source pass on opposite side of the central column, through the open space and outwardly from the rotor to a pair of oscillating mirrors which intersect light beams that, in this embodiment, have passed through two different bottles and these mirrors reflect the light beams which are modulated by the bottle walls and flaws and contaminants thereon, toward the detectors.
Another embodiment, especially applicable to machines having rotors of lesser diameter than the one mentioned in the preceding paragraph, also has the source of two light beams that pass through respective bottles on the radially outward side of the rotor. In this case, where the transported bottles occupy a major part of the circular path through which they are conveyed, the two light beams project past opposite sides of the central column. In this case, there are two oscillating mirrors and a pair of photodetector or image receiving means that are mounted on the opposite side of the central column from the light source but within the circular path through which the bottles are conveyed.
In still another embodiment, where the rotor diameters are smaller than in either of the two preceding cases, the light source is again located radially outwardly from the circular path through which the bottles are conveyed. Only one bottle at a time is aligned with the beams but the beams are projected in two paths that diverge from each other thereby pass opposite sides of the central column. Mirrors are arranged on opposite sides of the central column to reflect the beams to respective detectors which will produce a reject signal if either of the beams is modulated by a flaw or contaminant. In this embodiment, as opposed to the two preceding embodiments, the bottles are not rotated about their vertical axes as they sweep through the light beam. Instead, the bottles are carried on a rotor which has shallow pockets for retaining them.
The various structural features which contribute toward increasing inspection accuracy and accessibility of the scanning system components will now be described in detail in reference to the drawings.